用神经网络学习非平衡哈密顿路径,实现更准确的玻尔兹曼采样。
Neural Non-Equilibrium Hamiltonian Monte Carlo for Corrected Boltzmann Sampling

- 通过训练神经网络学习非平衡哈密顿路径,生成可纠正的采样路径。
- 在双阱、格点ϕ⁴等模型上,路径重叠足够时能给出正确估计。
- 适合需要高精度采样的物理与分子模拟场景,尤其关注路径修正机制。
从非归一化玻尔兹曼密度中采样,需要能够全局转移概率质量并保留足够路径概率信息以进行统计修正的提议。我们提出神经非平衡哈密顿蒙特卡洛(NHMC),一种先训练后修正的可学习哈密顿采样器。从一个易处理的基分布出发,NHMC 学习向目标分布的随机哈密顿路径。训练完成后,学习到的提议参数固定;提议生成完整路径和终点配置,并利用记录的非平衡功进行统计修正。该无量纲广义功由正向提议路径与反向参考路径的概率比决定。训练时最小化其均值可减少路径空间的KL散度,并控制终点错配的上界。评估时,该量定义路径上的自归一化重要性权重(path-SNIS),用于估计归一化常数或自由能差,也提供路径空间独立的梅特罗波利斯-哈斯金斯接受率(path-IMH)。我们进一步推导出共享桥接往返的NHMC-MH核,并证明其配置空间转移保持玻尔兹曼目标分布。在双阱、有限体积ϕ⁴格点、紧致非阿贝尔规范场及伦纳德-琼斯团簇目标上,当路径重叠充分时,NHMC能给出校正估计;当重叠较差时,权重退化、接受率低、自相关长,暴露了提议失败。此外,我们还报告了使用分子动力学先验和学习力路径提议的分子内坐标可行性研究。
原文摘要 · Abstract (English)
Sampling from an unnormalized Boltzmann density requires proposals that move probability mass globally while retaining enough path-probability information for statistical correction. We introduce Neural Non-Equilibrium Hamiltonian Monte Carlo (NHMC), a train-then-correct learned Hamiltonian sampler. Starting from a tractable base distribution, NHMC learns stochastic Hamiltonian-style paths toward the target. Once training is complete, the learned proposal parameters are fixed; the proposal then generates complete paths and endpoint configurations, which are statistically corrected using the recorded non-equilibrium work. This dimensionless generalized work is determined by the probability ratio between the forward proposal path and a reverse reference path. During training, minimizing its mean reduces a path-space KL divergence and controls an upper bound on endpoint mismatch. During evaluation, the same quantity defines weights for self-normalized importance sampling on paths (path-SNIS), estimates normalizing constants or free-energy differences, and gives the acceptance ratio for path-space independent Metropolis--Hastings (path-IMH). We further derive a shared-bridge round-trip NHMC--MH kernel and prove that its configuration-space transition preserves the Boltzmann target. On double-well, finite-volume lattice $ϕ^4$, compact non-Abelian gauge, and Lennard--Jones cluster targets, the NHMC construction gives corrected estimates when path overlap is sufficient; when overlap is poor, weight degeneracy, low acceptance, and long autocorrelation expose proposal failure. We additionally report a molecular internal-coordinate feasibility study using a molecular-dynamics prior and learned-force path proposal.
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